An alternator is used as the drive source for driving the engine of an automobile and performs the necessary power generation for the automobile. The construction of such alternator was disclosed, for example, in Japanese patent publication No. Tokukai Hei 7-139550. FIG. 1 shows the alternator 1 described in that disclosure. A pair of rolling bearings 4 supports a rotating shaft 3 inside a housing 2 such that it rotates freely. A rotor 5 and a commutator 6 are located in the middle section of this rotating shaft 3. Also, there is a follower pulley 7 fixed to one end (right end in FIG. 1) of this rotating shaft 3 in the section that protrudes out from the housing 2. When assembled in an engine, an endless belt runs around this follower pulley 7 such that the rotating shaft 3 can be rotated and driven freely by the crankshaft of the engine.
Conventionally, a pulley that was simply fixed to the rotating shaft 3 was used as this follower pulley 7. However, recently, various kinds of pulley apparatuses with built-in one-way clutches have been proposed, and some have been used where in cases where there is a tendency for the running speed of the endless belt to be constant or to increase, power is transmitted freely to the rotating shaft from the endless belt, and in the case where there is a tendency for the running speed of the endless belt to decrease, the follower pulley rotates freely relative to the rotating shaft. For example, pulley apparatuses with built-in one-way clutches, having the functions described above, have been disclosed in Japanese patent publications Nos. Tokukai Hei 10-213207, 10-285873, 11-22753, and 11-63026. Moreover, the use of a roller clutch as the one-way clutch has also been known, such as described in each of the aforementioned disclosures.
FIGS. 2 to 6 show a previously known pulley apparatus with built-in roller clutch, such as described in these disclosures. This pulley apparatus with built-in roller clutch has a rotating member (or called a shaft member), or more specifically a sleeve 8, that fits around the outside of the rotating shaft 3 of the alternator 1 (see FIG. 1). Also, there is a pulley member, or in other words a follower pulley 7 located around this sleeve 8, such that it is concentric with the sleeve 8. Moreover, there is a pair of ball bearings 9a, 9b and a roller clutch 10 located in the space between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the follower pulley 7.
The sleeve 8 is formed generally into a substantially cylindrical shape and is fixed to the end of the rotating shaft 3 of the alternator 1 such that it rotates together with the rotating shaft 3. As shown in the example in the figure, in order to do this, a screw hole section 11 is formed around the inner peripheral surface in the middle section of the sleeve 8, and this screw hole section 11 is screwed together with a male screw section that is formed around the outer peripheral surface on the tip end of the rotating shaft 3. Also, a fitting hole section 12, having a hexagonal cross section, is formed on the inner peripheral surface on the tip end (left end in FIG. 2) of the sleeve 8 such that the tip end of a tool such as a hexagonal wrench can fit into this fitting hole section 12. Furthermore, the inner peripheral surface of the base end (right end in FIG. 2) of the sleeve 8 is a circular hole section 13 that freely fits tightly around the tip end of the rotating shaft 3 at a location closer to its middle section without lost motion. It is also possible to use other construction such as a spline joint, non-circular joint, or key joint so that the sleeve 8 does not rotate relative to the rotating shaft 3. Also, the center section of the outer peripheral surface of the sleeve 8 is a large-diameter section 14 that has a larger diameter than other sections.
On the other hand, the outer peripheral surface on the tip-end half of the follower pulley 7 is formed with a wave-shaped cross section in the width direction such that part of an endless belt, called Poly V-belt, can run around it. Also, a roller clutch 10 is located in the middle section in the axial direction of the space between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the follower pulley 7, and ball bearings 9a, 9b are located on both ends in the axial direction of this space such that they hold the roller clutch 10 on both sides in the axial direction.
The ball bearings 9a, 9b support radial loads and axial loads that are applied to the follower pulley 7 such that the follower pulley 7 can rotate freely with respect to the sleeve 8. Each of the ball bearings 9a, 9b comprises: an outer race 16 having an outer-raceway 15 of the deep-groove type formed around its inner peripheral surface; an inner race 18 having an inner-raceway 17 of the deep-grooved type formed around its outer peripheral surface; and a plurality of balls 19 located between the outer-raceway 15 and the inner-raceway 17, such that they can rotate freely. Also, the outer race 16 is fitted and fastened around the inner peripheral surface on both ends of the follower pulley 7, and the inner race 18 is fitted and fastened around the outer peripheral surface on both ends of the sleeve 8. Moreover, in this state, one surface in the axial direction of each inner race 18 comes in contact with the respective end surface (stepped surface) in the axial direction of the large-diameter section 14. Furthermore, seal rings 20 are located between the inner peripheral surface around both ends of the outer races 16 and the outer peripheral surface around both ends of the inner races 18 to cover the openings on both ends of the space where the balls 19 are located.
The roller clutch 10 transmits rotating force between the follower pulley 7 and sleeve 8 only when the follower pulley 7 tends to rotate in a specified direction with respect to the sleeve 8. In order to construct this kind of roller clutch 10, an inner clutch-race 21 is tightly fitted and fastened around the large-diameter section 14 of the sleeve 8. This inner clutch-race 21 is formed into a generally circular shape by performing plastic working, such as pressing steel plate like carburized steel, and a cam surface 22 is formed around its outer peripheral surface. In other words, the cam surface 22 can be formed around the outer peripheral surface by forming a plurality of concave sections 23, called ramp sections, around the outer peripheral surface of the inner clutch-race 21 such that they are uniformly spaced around in the circumferential direction as shown in FIGS. 3 and 5. In the example shown in the figures, a tapered concave beveled section 24 is formed around one end (left end in FIG. 2) around the inner peripheral surface of the inner clutch-race 21, and this beveled section 24 functions as a guide surface for when pressure fitting the inner clutch-race 21 around the outer peripheral surface of the large-diameter section 14.
On the other hand, an outer clutch-race 25 is tightly fitted and fixed in the middle section of the inside peripheral surface of the follower pulley 7, and at least the middle section in the axial direction of the inner peripheral surface of the outer clutch-race 25 that comes in direct contact with a roller 26 (described below) is a simple cylindrical surface. This kind of outer clutch-race 25 is also formed into a generally cylindrical shape by plastic working e.g. pressing steel plate like carburized steel plate, and inward facing flange sections 27a, 27b are formed on both ends in the axial direction of the outer clutch-race 25. Of the two flange sections 27a, 27b, the flange sections 27a (left section in FIG. 2) is formed in advance when making the outer clutch-race 25, so it has the same thickness as that of the cylindrical portion of the outer clutch-race 25. On the other hand, the flange section 27b (right section in FIG. 2) is formed after the roller 26 and clutch retainer 28 (described below) have been assembled on the inside in the radial direction of the outer clutch-race 25, so it is thin in material thickness.
Moreover, a clutch retainer 28 is fit around the outside of the inner clutch-race 21 such that it is impossible for it to rotate with respect to the inner clutch-race 21. A plurality of rollers 26, which together with the inner clutch-race 21 and the outer clutch-race 25 form the roller clutch 10, are held by the clutch retainer 28 such that they can freely roll and also move a little in the circumferential direction. This clutch retainer 28 is made of synthetic resin or plastic (for example, a synthetic resin such as polyamide 66, polyamide 46 or polyphenylene sulfide that is mixed with about 20% glass fibers) and is formed generally into a cage-like cylindrical shape, and as partly shown in FIG. 4, this clutch retainer 28 comprises a pair of ring-shaped rim sections 29, and a plurality of column sections 30 that connect these rim sections 29.
The sections that are surrounded on four sides by the inside surfaces of the rim sections 29 and the surfaces in the circumferential direction of the column sections 30 form pockets 31 for holding the rollers 26, respectively, such that they can freely roll and also move a little in the circumferential direction. Also, as shown in FIG. 5, protrusions 32 are formed at a plurality of locations on the inner peripheral surface of the rim sections 29 while concave sections 23 are formed on the outer peripheral surface of the inner clutch-race 21, and the protrusions 32 are fitted with the concave sections 23, so that the clutch retainer 28 is attached such that it cannot rotate with respect to the inner clutch-race 21.
Moreover, a substantially cylindrical space is formed between the outer peripheral surface of the cam surface 22 and the inner peripheral surface (cylindrical surface) in the middle section of the outer clutch-race 25. As shown in FIG. 6, springs 33 are attached to one of the sides in the circumferential direction of the column sections 30 of the clutch retainer 28, respectively. These springs 33 that are attached to each of the column sections 30 elastically press the rollers 26, that are held in the pockets 31, in the same circumferential direction of the clutch retainer 28 toward the section having a narrow width in the radial direction (toward the right, or in the clockwise direction of FIG. 5), respectively. In the example shown in the figure, flat springs made of spring steel plate and bent on both ends in a substantially hook shape are used as the springs 33, however it is also possible to use synthetic resin springs that are formed together in a single piece with the clutch retainer 28.
Also, as to the flange sections 27a, 27b of the outer clutch-race 25, both of the ends in the axial direction of the clutch retainer 28 come very close to and face the inside surfaces of these flange sections 27a, 27b, and this prevents the clutch retainer 28 from moving in the axial direction. However, instead of this construction, another construction for preventing the clutch retainer from moving in the axial direction has been known, in which a plurality of stepped sections are formed around the outer peripheral surface of a shaft member such as a sleeve to fit with parts of the clutch retainer, such as disclosed in Japanese patent publications No. Tokukai Hei 11-22753, No. Tokukai 2001-165201, etc.
When using a pulley apparatus with built-in roller clutch that is constructed as described above and there is a tendency for the follower pulley 7 and sleeve 8 to relatively rotate to a specified direction, or in other words, when the follower pulley 7 tends to rotate relative to the sleeve 8 in the direction that the springs 33 push the rollers 26 (to the right or clockwise in FIG. 5), the rollers 26 bite into the sections having a narrow width in the radial direction in the substantially cylindrical space. Also, the follower pulley 7 cannot rotate relative to the sleeve 8 (this is called locked state). On the other hand, when the follower pulley 7 and sleeve 8 rotate in a direction opposite to the specified direction, or in other words, when the follower pulley 7 tends to rotate relative to the sleeve 8 in the direction (to the left or counterclockwise direction in FIG. 5) opposite the direction that the springs 33 push the rollers 26, the rollers 26 move against the elastic force of the springs 33 toward the sections having a large width in the radial direction in the substantially cylindrical space, and the follower pulley 7 can rotate freely relative to the sleeve 8 (this is called overrun state).
There are the following two reasons for using a pulley apparatus with built-in roller clutch constructed as described above in an alternator. The first reason is to increase the life of the endless belt. For example, when the drive engine is a diesel engine or direct-injection gasoline engine, there are large changes in rotation angle speed of the crankshaft when rotating at low rpm such as during idling. As a result, the running speed of the endless belt that runs around the follower pulley also changes small. On the other hand, rotation of the rotating shaft 3 of the alternator that is rotated and driven by the endless belt via the follower pulley does not change so suddenly due to the inertial mass of the rotating shaft 3 and the rotor etc. fixed to the rotating shaft 3. Therefore, when the follower pulley is simply fixed with respect to the rotating shaft, there is a tendency for friction to occur in both directions between the endless belt and follower pulley due to changes in the rotation angle speed of the crankshaft. As a result, stress is applied repeatedly in differing directions on the endless belt that rubs against the follower pulley, which makes it easy for slipping to occur between the endless belt and the follower pulley, or becomes the cause of decreased life of the endless belt.
Therefore, by using the pulley apparatus with built-in roller clutch described above as the follower pulley, when there is a tendency for the running speed of the endless belt to be fixed or to increase, the rotation force is freely transmitted from the follower pulley to the rotating shaft 3, and conversely, when there is a tendency for the running speed of the endless belt to decrease, the follower pulley rotates freely with respect to the rotating shaft. In other words, when there is a tendency for the running speed of the endless belt to decrease, the rotation angle speed of the follower pulley becomes slower than the rotation angle speed of the rotating shaft, so as to prevent strong rubbing from occurring at the area of contact between the endless belt and the follower pulley. In this way, the direction of the stress that acts on the section of rubbing between the endless belt and the follower pulley becomes constant, and it is possible to prevent slipping between the endless belt and the follower pulley, or to prevent a decrease in the life of the endless belt.
The second reason is to improve the power generating efficiency of the alternator. The drive engine of the automobile rotates and drives the rotating shaft 3, to which the alternator rotor is fixed, by way of the endless belt and follower pulley. When using a fixed type follower pulley and the rpm of the drive engine decreases suddenly, the rpm of the rotor also decreases suddenly, as well as does the amount of power generated by the alternator. However, when using a pulley apparatus with built-in roller clutch as described above as the follower pulley of the alternator, the rpm of the rotor decreases gradually due to inertial forces and power generation continues during this time, even though the rpm of the drive engine decreases suddenly. As a result, it is possible to more efficiently use the kinetic energy of the rotating shaft and rotor and to increase the amount of power generated by the alternator more than when using a fixed-type follower pulley.
The explanation above is made for the case of when the pulley apparatus with built-in roller clutch was located on the side of the follower pulley, however, similar function and effects can be obtained when a pulley apparatus with built-in roller clutch, having the same construction as described above, is located on the end of crankshaft on the drive side.
In the aforementioned documents that describe a prior art pulley apparatus with built-in roller clutch, including the prior art construction described above, the construction is capable of maintaining the durability and reliability of the pulley apparatus with built-in roller clutch, however there was nothing particularly mentioned about a method for more efficiently assembling this pulley apparatus with built-in roller clutch.
Taking this into consideration, it is an object of this invention to provide a pulley apparatus with built-in roller clutch that is sufficiently durable and reliable, and an assembly method that makes it possible to easily assemble that pulley apparatus with built-in roller clutch.